As the search for oil and gas deposits below the sea bed continues, exploration and production equipment are utilized in deeper and deeper waters. While subsea exploration has typically been conducted in waters having a depth less than 300 meters, exploration and production are now moving to depths greater than this. Systems are known for operating at such depths which include a submarine base on the sea bed, a plurality of risers extending upwardly from the base, a submerged buoyant structure coupled to the risers and keeping them in tension and a catenary flowline bundle coupled between the buoyant structure and a surface vessel. In this assembly, the production wellheads are conveniently mounted on the buoyant structure which is spaced below the surface of the water a sufficient depth, such as 50 meters, to avoid the problems of waves, winds, currents, vessels and storms. In addition, the buoyant structure can easily be reached by a diver if necessary. Examples of these systems are shown in U.S. Pat. Nos. 4,170,266 to Fayren and 4,182,584 to Panicker et al.
Although these systems are advantageous in very deep waters, various problems need to be overcome in order to use them for effective exploration and production. For example, a quick, accurate and repeatable connection of the catenary flowline bundle to the submerged buoyant structure is necessary. In addition, it is advantageous to couple control lines as well as the flowlines to the buoyant structure so that, for example, valves on the wellheads can be easily activated. Moreover, it is highly advantageous to connect the flowlines and control lines to the buoyant structure remotely without significant diver assistance.
While there are various prior art devices that deal generally with these problems, there is still room and need for improvement. Examples of these prior art devices are disclosed in U.S. Pat. Nos. 3,339,632 to Lewis; 3,551,005 to Brun; and 3,604,731 to Peterson, as well as the two patents cited above.